Tamping device



P 27, 1966 a. E. GRANT ETAL 3,274,908

TAMPING DEVICE Filed July 22, 1964 2 Sheets-Sheet 1 wnllllllll lllw INVENTORS GERALD E. GPA/V7 BY EucEA/E L. H51. TON

ATTORNEYS p 1966 G. E. GRANT ETAL 3,274,908

TAMPING DEVICE Filed July 22, 1964 2 Sheets-Sheet z J6 J6 f4 45 fig - INVENTORS i GERALD 5. GRANT ZZZ EUGENE L. HELTON vhf 3Q TTORNEYS United States Patent 3,274,908 TAMPING DEVICE Gerald E. Grant, East Peoria, and Eugene L. Helton, Peoria, 111., assignors to Caterpillar Tractor Co., Peoria, 11]., a corporafion of California Filed July 22, 1964, Ser. No. 384,388 Claims. (Cl. 94-48) This invention relates to improvements in tamping devices and more particularly to tamping devices of the type which have a replaceable tamping foot.

In achieving a desired degree of compaction of various earth materials such as crushed rock or dirt, those concerned with designing machinery which fulfills this function have proposed various tamping devices, commonly refered to as sheep foot tampers, having a high degree of penetration which is accomplished by providing a relatively small area for the ground engaging surface. Since such materials are highly abrasive, the life span of deep penetrating tamping devices is very short thus increasing compacting costs. Additionally tamping devices which have a high degree of penetration not only have a short life but require more power to rotate the wheels upon which these tamping devices are mounted.

Tamping apparatus of the type disclosed herein are associated with a self-powered vehicle whose wheels are formed with a cylindrical steel tread on whose periphery are mounted a large number of circumferentially spaced tamping devices. It can be appreciated that the motive power of such vehicles would depend upon the depth of penetration of the tamping feet and to some extent the material which is being tamped. When it is considered that several hundred tamping feet are provided with each of these vehicles and the fact that the tamping feet are welded to the periphery of the wheels, replacement of the tamping feet from the standpoint of parts cost, labor costs, and time required to efiect such replacement greatly reduces the productive time of self-propelled tampers. In order to reduce such costs, tamping devices are provided with a detachable tamping foot which is releasably secured to a pedestal which in turn is welded to the periphery of the wheels.

Although tamping devices with replaceable feet have been reasonably successful in solving the above mentioned problems, they are still subject to a very rapid rate of wear since they have been designed for deep penetration.

Tamping devices with replaceable feet are attached to the pedestal by providing cooperating locking tapered surfaces onthe pedestal and on the foot with means for holding the tamping foot in engagement with the pedestal which ordinarily consists of a pin or a bolt. Disassembly of such a construction is usually accomplished by removing the pin or bolt and then driving a wedge or a drift pin which disestablishes locking engagement of the tamping foot from the pedestal. It is to be appreciated that after a period of use the taper on the foot expands causing the locking pin to become bent or deformed and thereby making removal of the pin quite difficult.

In precluding such dilficulties it is a feature of this invention to provide a pedestal which supports the tamping foot so that easy removal thereof may be accomplished without the use of drift pins or wedges.

In accordance with another feature of this invention, the mounting pedestal which is welded to the wheels of the tamping vehicle, has a projection of reduced dimensions which is completely enclosed by the replaceable foot in order to preclude abrasion wear of the pedestal.

In the interest of providing an easy method of replacing the tamping foot, this invention provide aligned bores, formed on the replaceable foot and on the pedestal, within which is disposed a cylindrical pin that is closely slidably received in axially aligned bores formed through "ice opposite sides of the replaceable foot and is spaced from the bore formed in the pedestal allowing a certain amount of freedom for the pin in the pedestal-bore. Intermediate the ends of the pin, a groove is formed within which a resiliently biased complementary shaped plate is located to define a detent holding the pin against axial movement. In this manner bending and consequent jamming of the pin in the bores is avoided.

Accordingly it is an object of this invention to provide a new and improved tamping device.

Another object of this invention is to provide a tamping device which includes a replaceable foot mounted for ,easy removal from the mounting pedestal and which placeable foot tamping device having cooperating surfaces being held in abutting relationship by a resiliently biased pin connection.

With the foregoing objects in view, together with such other objects and advantages as may subsequently appear,

the following describes one form which the invention may take in practice.

In the drawings:

FIG. 1 is a side elevation of the tamping device constructed in accordance with the principles of this invention, shown mounted on a fragmentary portion of a compacting wheel.

FIG. 2 is an enlarged disassembled perspective of the tamping device of FIG. 1.

FIG. 3 is a central section taken substantially along the line III-III of FIG. 4. i

FIG. 4 is an end view partially in section showing the details of construction of the retaining means.

Referring now to FIG. 1 there is shown a fragmentary portion of a compacting wheel designated by the numeral 10 on whose periphery are mounted, in circumferentially spaced relation, tamping devices 12. The tamping devices comprise a generally pyramidal shaped member 14 secured, preferably by welding, to the peripheral surface of the compacting wheel 10. This member 14 has a smaller projecting pyramidal portion upon which is releasably mounted a replaceable camping foot 16. The tamping foot 16 is hollow in form and is shaped to receive the projecting pyramidal shaped portion of the member 14 and is held in the position shown in FIG. 1 by retaining member 18, which is in the form of a .pin extending through axially aligned bores in the tamping foot and in the projecting portion of the base member '14.

As shown in FIG. 2 the member 14 includes a lower base portion 20 and a projecting pyramidal portion 22, of reduced dimensions through which is formed a hole 24 for receiving-the retaining member 18. .The portion 22 has a generally fiat end wall 26 formed by two flat surfaces joined at a slight angle which define an apex located generally centrally thereof. Another hole 28, located on an axis substantially normal to the axis of the hole 24, is formed in the portion 22 and this hole communicates with the hole 24 (see FIG. 3). The tamping foot 16 is formed with a hollow interior being of substantially the same shape as the projecting portion 22 and of sufficient depth to completely shroud or enclose the portion 22. The inside dimensions of the hol- 10w interior of the foot are greater than the dimensions of the projecting pyramidal portion so that the foot is supported solely on the end wall 26 when assembled thereon. Tamping foot 16 has bores 30 formed in opposite walls thereof for slidab ly receiving the pin member 18 in a titted relationship.

When the tamping foot 16 is located in assembled relation relative to the portion 22, as shown in FIG. 1, the opposed outer surfaces of the foot define continuation of the surfaces of the member 14; however, the inner edges of the foot 16 are located in slightly spaced relation to a surface r32 which defines the transition zone between the base 20 and the projecting portion 22.

The interior surface of the tamping food 16 and the surface of the portion 22 are formed generally similar in shape as indicated by the section shown in FIG. 3. The tamping foot 16 is freely received on the portion 22 because of the oversize dimensions of the hollow inter-ior in non-locking relationship in order to achieve rapid assembly and disassembly. Because the foot is supported only on the end wall 26 it is impossible for the foot to become wedged on the end of the projecting portion 22. However, the end wall surfaces of the portion 22 and those at the base of the tamping foot 16 are held in forceable engagement when the foot 16 and the portion 22 are in assembled relationship. As shown in FIG. 3, the portion 22 comprises upwardly extending sloping wall port-ions 34, and the curved portions 36 which continue upwardly and inwardly to define upper walls 38. A counterbore 40, coaxial with the bore 28, is provided for freely receiving a short boss (dowel) 42 formed on the interior of the tamping foot 16. The tamping foot 16 has downwardly extending end walls 44 and side walls 45 terminating at 46, in close adjacency to the transition surface 32, which substantially completely encloses the walls 34. The inner surfaces of the walls 44 are formed with arcuate surface 48, of a greater radius than the adjacent radial portions 36, that smoothly merges with planar surfaces 50 at the base of the foot that contact the walls 26 of the portion 22. Particular attention is drawn to the fact that the walls 44 are in spaced relation with respect to the outer surface of the sloping wall portions 34, thus precluding locking engagement of these tapered walls. It is also to be noted that the boss 42 is of sufiiciently reduced diameter with respect to the counterbore 40 so that a circumferential space is defined.

The tamping foot 16 merely rests on the portion 22 in such a manner so that only the surfaces 26 on the portion 22, and the surfaces 50, on the tamping foot 16, are in contact. It can be seen, therefore, that the tamping foot 16 is freely mounted on the portion 22. Thus the end wall 26 and mating surfaces 50 are the only load bearing surfaces between the foot and the member 14.

In accordance with another feature this invention, the

'pin '18 is associated with a detent mechanism, which not only holds the pin against axial displacement when disposed in the aligned holes 24 and 38, but is arranged to retain the tamping foot 16 on the base member 14 by holding the surfaces 26 and 50 in forceable engagement. As shown in FIGS. 3 and 4 the upper end of the bore 28 has a plug 52 secured therein in any suitable manner,

to which is attached, preferably by bonding, a suitably when it is in a relaxed condition in order to provide for displacement of the rubber material when it is subjected to compression imparted by the pin 18. It is apparent that the force exerted by the rubber-like member 54 in urging the plate 56 toward the pin 18 constitutes, in combination with the arcuate groove 60, a detent mechanism which releasably holds the pin 18 against axial movement. It is to be particularly noted that the co-axial bores 30 formed in tamping foot 16 of such a size to closely slidably receive the pin 18 in a snugly tfitted relationship Whereas the bore 24 is relatively larger than the diameter of the pin thereby allowing radial movement of the pin with respect to the bore 24.

With the parts in assembled relation as shown in FIGS. 3 and 4, the bias imparted by the resilient member 54 to the plate 56 forces the pin '18 downwardly, and by virtue of the closely fitted bore -30, the tamping foot 16 is also urged downwardly since the pin 18 is free to move in the bore 24. As a result the surfaces 26 and 50 are held in forceable engagement. It should be apparent that disassembly of the tamping foot 16 from the projecting portion .22 is effected by imparting an axial force to the pin I18, for example, by using a drift pin and a hammer, to drive the pin out of the registered bores whereupon the resilient member 54 assumes a relaxed condition and it is merely necessary to lift the foot 16 from the projecting portion 22 to remove it.

In addition to the fact that the tamping foot device of this invention provides a tamping foot that is easily removable from a mounting pedestal, the end Walls 44 and the side walls 45 serve to completely shroud the portion 22 in order to preclude abrasion wear but do not bear thereupon. v

The ground engaging area of the tamping foot 16 has been chosen to be large enough so that excesive penetration of the tamping foot is precluded in order to reduce the rolling resistance and consequently the power required to propel the tamping machine over the ground. It is to be appreciated that in order to achieve economical operation compromises must be made between the rate of compaction, which is determined by the depth of penetration of the foot, and the number of passes which can be made per unit time. With a high penetration depth the life of the tamping feet is severely reduced thus increasing the overall time required to tamp a specified area which raises the cost of tamping a selected area. This invention reflects such a compromise while at the same time the cost of compaction is reduced to an absolute minimum.

Thus by providing a tamping device having a relatively shallow penetration and a replaceable ea-sily detachable foot, this invention results in a structure which reduces the power for operating a self-propelled tamper and the overall time for compacting since replacement of worn feet is readily accomplished.

Although one form of this invention has been shown and described, it is to be appreciated that various changes and modifications can be made without departing from the spirit of the invention, the scope of which is indicated by the following claims.

We claim:

1. A tamping device comprising an elongated support member having a base portion and a projecting portion with inwardly offset side walls terminating at angularly related planar top surfaces, a hollow tamping foot formed to be freely received on said projecting portion and including angularly related planar surfaces which mate in contact with the first mentioned planar surfaces, said tamping foot being formed to substantially enclose said inwardly offset side walls, a retaining member located through axially aligned openings in said projecting portion and in said foot for releasably holding said foot on said support member, said opening in said projecting portion being of suflicient size to allow said retaining mem her a limited degree of transverse movement whereas the openings in said foot closely receive said retaining member, a detent mechanism located outboard of said opening in said projecting portion including a resiliently biased member engageable with a peripheral portion of said retaining member for urging the angularly mated surfaces on said projecting portion and on said tamping foot in forceable contact.

2. A tamping device comprising an elongated support member having a base portion and a projecting portion with inwardly offset side walls terminating at angularly related planar top surfaces, a tamping foot formed with walls which enclose said projecting portion and including inner angularly related transversely extending planar surfaces for mating engagement with said top surfaces, said walls being located in spaced relation to said offset side walls of said projecting portion when the planar surfaces on said projecting portion and said foot are in engagement, a retaining member located through axially aligned openings in said projecting portion and in the walls of said tamping foot for releasably holding said foot on said support member, said opening in said projecting portion being of suificient size to allow said retaining member a limited degree of transverse movement whereas the openings in the walls of said tamping foot closely receive said retaining member, a detent mechanism located outboard of said opening in said projecting portion including a resiliently biased member engageable with a peripheral portion of said retaining member for urging said retaining member in such a direction so that the angularly mated surfaces on said projecting portion and on said tamping foot are brought into forceable engagement.

3. A tamping device securable to the circumferential periphery of cylindrical bodies used for compacting and having a replaceable foot comprising;

(a) an elongated support member having a base portion securable to a compacting device and a projecting portion with inwardly offset side walls, said projecting portion terminating at a top bearing surface;

(b) a hollow tamping foot having a recess freely fitting on said projecting portion and a surface mating with said top bearing surface in a non-wedging engagement, said tamping foot being formed to substantially enclose said inwardly offset walls of said projecting portion;

(0) a retaining member located through axially aligned openings in said projecting portion and in said foot to secure said foot on said portion, said openings in said projecting portion being of sufficient size to allow said retaining member a limited degree of transverse movement therein and said openings in said foot closely receiving said retaining member; and

(d) a detent mechanism located outboard of said openings in said projecting portion including a resilient biased member engageable with the peripheral portion of .said retaining member within said projecting portion and operable to urge said retaining member inwardly toward said base whereby said top bearing surface and said surface mating therewith in said foot are forced into engagement.

4. The tamping device as defined in claim 3 wherein the top bearing surface is composed of angular related planar surfaces.

5. The tamping device as defined in claim 3 wherein the foot has a positioning dowel in the surface which mates with the top bearing surface of the projecting portion of the support member, and said top bearing surface has a recess for receiving said dowel to prevent lateral movement of the said surfaces.

References Cited by the Examiner UNITED STATES PATENTS JACOB L. NACKENOEF, Primary Examiner. 

1. A TAMPING DEVICE COMPRISING AN ELONGATED SUPPORT MEMBER HAVING A BASE PORTION AND A PROJECTING PORTION WITH INWARDLY OFFSET SIDE WALLS TERMINATING AT ANGULARLY RELATED PLANAR TOP SURFACES, A HOLLOW TAMPING FOOT FORMED TO BE FREELY RECEIVED ON SAID PROJECTING PORTION AND INCLUDING ANGULARLY RELATED PLANAR SURFACES WHICH MATE IN CONTACT WITH THE FIRST MENTIONED PLANAR SURFACES, SAID TAMPING FOOT BEING FORMED TO SUBSTANTIALLY ENCLOSE SAID INWARDLY OFFSET SIDE WALLS, A RETAINING MEMBER LOCATED THROUGH AXIALLY ALIGNED OPENINGS IN SAID PROJECTING PORTION AND IN SAID FOOT FOR RELEASABLY HOLDING SAID FOOT ON SAID SUPPORT MEMBER, SAID OPENING IN SAID PROJECTING PORTION BEING OF SUFFICIENT SIZE TO ALLOW SAID RETAINING MEMBER A LIMITED DEGREE OF TRANSVERSE MOVEMENT WHEREAS THE OPENINGS IN SAID FOOT CLOSELY RECEIVE SAID RETAINING MEMBER, A DETENT MECHANISM LOCATED OUTBOARD OF SAID OPENING IN SAID PROJECTING PORTION INCLUDING A RESILIENTLY BIASED MEMBER ENGAGEABLY WITH A PERIPHERAL PORTION OF SAID RETAINING MEMBER FOR URGING THE ANGULARLY MATED SURFACES ON SAID PROJECTING PORTION AND ON SAID TAMPING FOOT IN FORCEABLE CONTACT. 